Courtship signals and mate choice of the flies of inbred Drosophila montana strains

We studied genetic variation in fly mating signals and mate choice in cross es within and between inbred strains of Drosophila montana. Male songs and the cuticular hydrocarbons of both sexes as well as some of the flies' beha vioural traits differed significantly between strains. This did not, howeve r, cause sexual isolation between strains. In fact, courtship was shorter i f the female was courted by a male of a foreign strain than when courted by their own male. Heterosis was found for courtship duration and the carrier frequency of male song. Diallel analysis of male song revealed additive ge netic variation in four out of the five traits studied. Two traits showed d ominance variation and one of these, carrier frequency, expressed unidirect ional dominance with alleles for higher carrier frequency being dominant. D irection of dominance in carrier frequency was the same as the direction of sexual selection exercised by D. montana females on this trait, which sugg ests that sexual selection could be a driving force in the evolution of son g towards a higher carrier frequency.